Fuel delivery systems in internal combustion engines may experience various conditions in which vapors may form in the fuel lines. For example, fuel delivery systems may experience leaks in which ambient air enters the fuel delivery system. Likewise, fuel vapors may form at increased temperatures.
One approach to deal with vapor formation is described in JP 06-146984. In this system, a fuel pressure detected by a fuel pressure sensor is stored at the time of starting. A deviation between a fuel pressure, after a period of time elapses, and the initial fuel pressure is determined. The deviation is corrected according to the initial fuel pressure and a power source voltage of a fuel pump. Then, the amount of vapor is estimated based on the corrected deviation, and the correction of fuel pressure and injection pulse width is provided.
The inventors herein have recognized a disadvantage with such an approach. In particular, in direct injection systems utilizing a first, lower pressure, and second, higher pressure, fuel pump, the initial fuel pressure at starting may not correctly identify fuel vapor generation. Further still, such an approach may not properly identify and/or differential leaks from vapor formation.
As such, in one approach, a method for operating a fuel delivery system with a first pressure pump fluidly coupled to a second higher pressure pump and a fuel rail may be used. The method includes adjusting pump operation of at least one of the first and second pumps during engine starting, the adjustment based on engine starting conditions. When pressure rise during the start is correlated to an expected response, the method further includes adjusting pump operation independent of the measured fuel pressure, and when pressure rise during the start is less than the expected response, the method further includes adjusting pump operation based on the measured fuel pressure.
In this way, it is possible to accurately and robustly respond to various engine starting situations including vapor formation, leaks, etc. For example, when the pressure rise correlates to an expected response, one or both of the pumps may be adjusted during the start, based on the measured pressure, to provide improved control operation and better consistency in injection pressure for a first or subsequent injection. Alternatively, when the pressure rise is below the expected response, one or both pumps may be adjusted independent form the measured pressure, since the pressure measured may not provide an accurate indication of injection operation. Thus, the effects of vapor formation and/or leaks may be mitigated.